I would have put that ZED would be less now days because most airlines now charge for buddy passes. But, a quick look at airlines I have access to (not AA) they are basically the same price between a ZED (on AA) and Buddy (on UA). Using a buddy pass the person issuing it would have better access for checking loads.

Depending on how the buddy passes are issued, as one way, per leg, round trip and if you are charged before or after you use them you could always use the buddy passes and get a ZED on a different carrier for a back up.

Also, I would expect buddy passes to be before ZED on most airlines. Also, upgrading to a higher class on a buddy pass is different between carriers.

Really need to ask FA friend (or maybe someone here with AA) boarding priority/upgrading class and cost for the buddy pass.

Tony